1. Field of the Invention
The present invention relates to a bonding method and a bonding apparatus.
2. Description of the Related Art
In recent years, a method of bonding a semiconductor chip and a package substrate with bumps is being watched with interest as a method of high-density mounting of the semiconductor chip on the package substrate. Where the above method is used to produce a semiconductor device, a semiconductor chip and a package substrate are bonded with bumps by, for example, disposing the semiconductor chip, on which bumps are formed, on the package substrate as opposed to the package substrate and melting the bumps by heating the semiconductor chip and the package substrate.
Meanwhile, the semiconductor chip with an LSI which is highly sophisticated when miniaturized has a multilayer wiring structure, and an interlayer insulating film having a low dielectric constant and low resistance metal wiring of, for example, copper are used for the semiconductor chip. But, the interlayer insulating film having a low dielectric constant is soft with a mechanical strength (a modulus of elasticity) of 1/10 or less in comparison with that of a conventionally used Si oxide film and poor in adhesiveness with another insulating film material or metal material.
Therefore, when a semiconductor chip having a high-performance LSI is bonded to a package substrate with bumps by the above-described method, there are problems that high thermal distortion occurs at the bases of the bumps and their peripheries, and a crack or peeling of the film occurs by multilayer wiring.
Especially, a low dielectric constant interlayer insulating film material having a specific inductive capacity of less than 4.0 is also poor in adhesiveness, and the metal configuring the bumps is changed from a lead (Pb) based material to a tin (Sn) based material considering environmental problems, so that the melting point of the bump material is increased from 120 to 225° C., and the above-described problems tend to occur.
Therefore, it is essential to reduce the thermal distortion in bonding a semiconductor chip having multilayer wiring comprising a low dielectric constant interlayer insulating film and a package substrate. There is also a known method that a semiconductor chip and a package substrate are bonded with bumps by placing the semiconductor chip, on which the bumps are formed, on the heated package substrate to melt the bumps. But, it does not provide effective measures to decrease thermal distortion because the above-described large thermal distortion is caused at the bases of the bumps and their peripheries because of contraction in a package substrate cooling process.
There is also disclosed a method of bonding a semiconductor chip and a package substrate with bumps by heating contact portions between the bumps and the package substrate with infrared rays or light such as laser beams to melt the bumps while preventing heat generated from a semiconductor chip heating device from escaping to the package substrate. But, this method has a problem that it greatly depends on the layout of the bumps because light becomes difficult to reach toward the center of the semiconductor chip.